This invention relates to apparatus and methods for loading particulate materials, such as mineral ore, from storage locations into transport vehicles. In particular, the present invention relates to improvements in methods and apparatus for use in loading materials such as calcined coke into cargo vessels by means of a loading chute.
Various types of loading chutes are known for transporting particulate materials into the hold of a transport vessel. Movement of the materials from a reservoir or storage area is typically effected via loading means (such as a belt conveyor) to a point above the transport vehicle. The chute is generally mounted so that the material is then allowed to fall through a discharge means into the chute.
The chute should be movable so as to prevent the burying of the end of the chute in the cargo. In addition, it is necessary to move the chute to permit "topping off" of the load by filling in the corners of the hold, as well as any other interstices in the mass of particulate materials.
A particularly advantageous type of chute has a telescoping structure, wherein a plurality of unit ducts of successively enlarged or decreased horizontal cross section are nested together. To maintain the ducts in association when the chute is fully extended, each duct may be provided for example with flanges, which cause the engagement of each duct with an adjacent duct. In a preferred arrangement, these flanges are of a design such that upon retraction of the chutes, for example by means of a pulley arrangement, the uppermost flanges stack up together. Such an arrangement of nesting ducts is disclosed, for example, in U.S. Pat. No. 3,926,290 to Isojima et al., the disclosure of which is hereby incorporated by reference. In practice, lift motor means is generally also provided to facilitate retraction of the telescoping duct assembly.
A particular problem encountered in the loading of many particulate materials, and in particular such products as calcined coke, is the generation of substantial quantities of fines and dust due to product degradation. Various solutions have been proposed to control the emission of dust discharged into the atmosphere as the material descends from the loading means into the transport vehicle. One common approach is to enclose the chute in a flexible conduit provided at one end thereof with, e.g., aspirator means. A countercurrent of air is generated by the aspirator means, whereby a significant portion of the dust may be collected and transported to a disposal means, such as a filter. Such a flexible conduit surrounding a loading chute and provided with a connection for aspirator means or the like is disclosed in U.S. Pat. No. 4,727,913 to Bliss, the disclosure of which is also hereby incorporated by reference.
While an arrangement as described in the aforementioned U.S. Pat. No. 4,727,913 as comprising part of the prior art thereto may be useful in suppressing dust discharged from the stream of falling material (especially when lower density bulk materials are loaded), it is further noted in the patent that in the case of denser bulk materials major portions of fines and dust are generated when the falling material impacts with the pile being deposited in the transport vehicle. Not only does this dust create potential environmental and safety hazards, but there is also a substantial likelihood of economic loss due to the degradation of product into fines and dust. To reduce the generation of dust at impact still further, U.S. Pat. No. 4,727,913 proposes the use of first and second tubular members coaxially disposed within a central hopper at the discharge end of a loading chute, whereby the flow of particulate matter is retarded in bottleneck fashion and material forced to pile up within the hopper is ultimately discharged through annular spaces between the hopper and first tubular member and/or the first and second tubular members, respectively.
With respect to coke, it has been determined that particle breakage is a direct function of the distance over which the material drops during the loading process. The amount of fines generated during a simulated loading process varied from 0% at zero fall height to about 35% at 120 feet. Significantly, about one-half the total degradation occurring at a 120 foot drop occurred in drop heights below 25 feet; thus, even small drop heights are significant contributors to size degradation.
Whereas a dust suppressing device as proposed in U.S. Pat. No. 4,727,913 may be useful in deflecting excess bulk material falling through a loading chute and reducing its velocity prior to its impact with the pile of material in the transport vehicle being loaded, such an arrangement still does not address the problem of excessive drop distances. Indeed, the device as described in the patent merely changes the point of impact of the particulate materials from the floor of the transport vehicle to an internal location in the loading chute arrangement. Even with this modification, the drop distance for the particulate material being loaded into the transport vehicle remains essentially the same: approximately 70 feet from the downspout to the bottom of the hold of the ship. As a consequence, a dust suppressing device in accordance with U.S. Pat. No. 4,727,913 would be useful primarily in controlling any dust generated, rather than in actually preventing the generation of fines and dust.
Accordingly, it is an object of the present invention to permit the loading of particulate materials, in particular calcined coke, onto transport vehicles in manner such that product degradation is substantially minimized.